Typical concrete wall structures are fabricated using concrete masonry units (CMU's—otherwise referred to as concrete blocks) that are positioned in courses atop a foundation and joined to one another by mortar. Ordinary CMU's include planar front and rear faces and, often, two or three spaced webs extending between the front and rear faces. The webs define one or two voids extending fully from top to bottom of the CMU. Outermost webs may comprise planar or recessed end faces of the CMU. The CMU is typically formed from cast concrete or other materials.
Building a wall using CMU's is a time-consuming process that is best undertaken by a skilled tradesperson, such as a mason. Once a level foundation has been prepared, the mason must arrange CMU's in level and plumb courses. The process of building is complex because the mason must use mortar both as a positioning and bonding agent. The consistency of the uncured mortar and the strength of the mortar, when dry, have a major impact on the quality and strength of the resulting wall.